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<h2><span class="refentrytitle">Macro BOOST_CONTRACT_FUNCTION</span></h2>
<p>BOOST_CONTRACT_FUNCTION — Program contracts that can be completely disabled at compile-time for (non-public) functions. </p>
</div>
<h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2>
<div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// In header: &lt;<a class="link" href="reference.html#header.boost.contract_macro_hpp" title="Header &lt;boost/contract_macro.hpp&gt;">boost/contract_macro.hpp</a>&gt;

</span>BOOST_CONTRACT_FUNCTION()</pre></div>
<div class="refsect1">
<a name="idm45885982183680"></a><h2>Description</h2>
<p>This is used together with <code class="computeroutput"><a class="link" href="BOOST_CO_idm45125847669680.html" title="Macro BOOST_CONTRACT_PRECONDITION">BOOST_CONTRACT_PRECONDITION</a></code>,  <code class="computeroutput"><a class="link" href="BOOST_CO_idm45125847658000.html" title="Macro BOOST_CONTRACT_POSTCONDITION">BOOST_CONTRACT_POSTCONDITION</a></code>, <code class="computeroutput"><a class="link" href="BOOST_CONTRACT_EXCEPT.html" title="Macro BOOST_CONTRACT_EXCEPT">BOOST_CONTRACT_EXCEPT</a></code>, and <code class="computeroutput"><a class="link" href="BOOST_CONTRACT_OLD.html" title="Macro BOOST_CONTRACT_OLD">BOOST_CONTRACT_OLD</a></code> to specify preconditions, postconditions, exception guarantees, and old value copies at body that can be completely disabled at compile-time for (non-public) functions:</p>
<pre class="programlisting"><span class="keyword">void</span> <span class="identifier">f</span><span class="special">(</span><span class="special">...</span><span class="special">)</span> <span class="special">{</span>
    <span class="identifier">BOOST_CONTRACT_OLD_PTR</span><span class="special">(</span><span class="identifier">old_type</span><span class="special">)</span><span class="special">(</span><span class="identifier">old_var</span><span class="special">)</span><span class="special">;</span>
    <span class="identifier">BOOST_CONTRACT_FUNCTION</span><span class="special">(</span><span class="special">)</span>
        <span class="identifier">BOOST_CONTRACT_PRECONDITION</span><span class="special">(</span><span class="special">[</span><span class="special">&amp;</span><span class="special">]</span> <span class="special">{</span> <span class="comment">// Optional.</span>
            <span class="identifier">BOOST_CONTRACT_ASSERT</span><span class="special">(</span><span class="special">...</span><span class="special">)</span><span class="special">;</span>
            <span class="special">...</span>
        <span class="special">}</span><span class="special">)</span>
        <span class="identifier">BOOST_CONTRACT_OLD</span><span class="special">(</span><span class="special">[</span><span class="special">&amp;</span><span class="special">]</span> <span class="special">{</span> <span class="comment">// Optional.</span>
            <span class="identifier">old_var</span> <span class="special">=</span> <span class="identifier">BOOST_CONTRACT_OLDOF</span><span class="special">(</span><span class="identifier">old_expr</span><span class="special">)</span><span class="special">;</span>  
            <span class="special">...</span>
        <span class="special">}</span><span class="special">)</span>
        <span class="identifier">BOOST_CONTRACT_POSTCONDITION</span><span class="special">(</span><span class="special">[</span><span class="special">&amp;</span><span class="special">]</span> <span class="special">{</span> <span class="comment">// Optional.</span>
            <span class="identifier">BOOST_CONTRACT_ASSERT</span><span class="special">(</span><span class="special">...</span><span class="special">)</span><span class="special">;</span>
            <span class="special">...</span>
        <span class="special">}</span><span class="special">)</span>
        <span class="identifier">BOOST_CONTRACT_EXCEPT</span><span class="special">(</span><span class="special">[</span><span class="special">&amp;</span><span class="special">]</span> <span class="special">{</span> <span class="comment">// Optional.</span>
            <span class="identifier">BOOST_CONTRACT_ASSERT</span><span class="special">(</span><span class="special">...</span><span class="special">)</span><span class="special">;</span>
            <span class="special">...</span>
        <span class="special">}</span><span class="special">)</span>
    <span class="special">;</span> <span class="comment">// Trailing `;` is required.</span>

    <span class="special">...</span> <span class="comment">// Function body.</span>
<span class="special">}</span>
</pre>
<p>This can be used to program contracts for non-member functions but also for private and protected functions, lambda functions, loops, arbitrary blocks of code, etc. For optimization, this can be omitted for code that does not have preconditions, postconditions, and exception guarantees.</p>
<p><code class="computeroutput">BOOST_CONTRACT_FUNCTION()</code> expands to code equivalent to the following (note that no code is generated when <code class="computeroutput"><a class="link" href="BOOST_CO_idm45125848498544.html" title="Macro BOOST_CONTRACT_NO_FUNCTIONS">BOOST_CONTRACT_NO_FUNCTIONS</a></code> is defined):</p>
<pre class="programlisting"><span class="preprocessor">#ifndef</span> <span class="identifier">BOOST_CONTRACT_NO_FUNCTIONS</span>
    <span class="identifier">boost</span><span class="special">::</span><span class="identifier">contract</span><span class="special">::</span><span class="identifier">check</span> <span class="identifier">internal_var</span> <span class="special">=</span>
            <span class="identifier">boost</span><span class="special">::</span><span class="identifier">contract</span><span class="special">::</span><span class="identifier">function</span><span class="special">(</span><span class="special">)</span>
<span class="preprocessor">#endif</span>
</pre>
<p>Where:</p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p><code class="computeroutput"><span class="bold"><strong>internal_var</strong></span></code> is a variable name internally generated by this library (this name is unique but only on different line numbers so this macro cannot be expanded multiple times on the same line).</p></li></ul></div>
<p>
</p>
<p><span class="bold"><strong>See Also:</strong></span></p>
<p> <a class="link" href="boost_contract/extras.html#boost_contract.extras.disable_contract_compilation__macro_interface_" title="Disable Contract Compilation (Macro Interface)">
        Disable Contract Compilation</a>,  <a class="link" href="boost_contract/tutorial.html#boost_contract.tutorial.non_member_functions" title="Non-Member Functions"> Non-Member Functions</a>,  <a class="link" href="boost_contract/advanced.html#boost_contract.advanced.private_and_protected_functions" title="Private and Protected Functions">
        Private and Protected Functions</a>,  <a class="link" href="boost_contract/advanced.html#boost_contract.advanced.lambdas__loops__code_blocks__and__constexpr__" title="Lambdas, Loops, Code Blocks (and constexpr)">
        Lambdas, Loops, Code Blocks</a> </p>
<p>
</p>
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</p>
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